May he himself take the money as a mudarabah investment—meaning, assign himself a share of the profit and trade with it?
The answer is no, because he said, “and he trades with it for him without charge.” Thus, if he says, “I wish to trade with the property of the legally restricted person, on the condition that I receive half of the profit, or a quarter of the profit, according to what is customary in the market,” he is not permitted to do so, because he is subject to suspicion. It is therefore not permissible for him to do this. However, as mentioned previously, if he says, “I will not trade except in return for a share, because this prevents me from conducting business with my own property,” we say: in that case, the matter is to be referred to the judge, who will assign him such a share as he considers appropriate.
His statement, “for a portion of the profit,” means an undivided share, for a mudarabah agreement is never valid with a specified share. Rather, it must be for a known undivided portion, as mentioned earlier.
For example, a man gives his wealth to someone as a mudarabah investment and says, “You shall have the profit of the month of Muharram, and I shall have the profit of the month of Safar.” This is specified and therefore impermissible. Likewise, if he says, “You shall have the profit from this commodity, such as sugar, while I shall have the profit from that commodity, such as rice,” this is impermissible because it is specified. And if he says, “You shall have one hundred riyals of the profit, and the remainder is mine,” this too is impermissible because it is specified. It must be an undivided share: one half, one quarter, or one sixth.
If he says, “Take this money as a mudarabah investment for a share,” it is not permissible, because the share is unknown; it must be known.
After the author mentioned that the guardian trades without charge, and that he may give the money to someone else as a mudarabah investment, he raises another issue: may an agent assign himself a wage for overseeing the property of the legally restricted person?